Background information on Aristotle:

Aristotle was born around 384 BC in Thrace. His father was the court physician to Macedon.
At the age of eighteen Aristotle travelled to Athens to learn at Plato's Academy and remained there until Plato's death around 20 years later. He subsequently became the tutor of the young Alexander the Great until Alexander reached the age of sixteen and became regent of Macedon. Bertrand Russell suggests that Aristotle had little if any practical influence on Alexander; however this is repudiated by historians such as JR Hamilton.
Aristotle lived out almost the rest of his life in Athens, probably writing most of his books and teaching during this period. After the death of Alexander the Great in Babylon the Athenians revolted against Macedon and turned on those who were seen to be friends of Alexander, forcing Aristotle into exile. He died the year after, in 322 BC.

Sources:
Russell, B. History of Western Philosophy. 1942 (2007 reprint)

Hamilton, J.R. Alexander the Great. 1974

Aristotle, like Thucydides, believed conflict between human beings in social life and politics to be inevitable. This theory influenced the theologian in the Middle Ages, St. Thomas Aquinas. In relation, Aristotle also believed that while strife and conflict are permanent features of comunal life (intra and inter communal strife) he believed the political community has the responsibility to act in accordance with the welfare of every human being -- not just its citizens. He did not think it appropriate to conquer and rule other regimes, because it is denying other human beings their freedom and status as fellow humans. He did however believe that defensive war was perfectly permissible.
Source? - xmarquez xmarquez Jul 24, 2008